Biomechanical and Electrophysiological Characterization of the Intact and Injured Peripheral Nerve

Lisa, A. Ferrara, MS
Edward C. Benzel, MD

It was the goal of this study to determine the changes in nerve conduction using a peripheral nerve model in response to biomechanical stimuli. The biomechanical stimuli were designed to mimic various compression injury pathologies to the peripheral nerve.This information may explain why there are poor responses to treatment after trauma to the nerves, as well as within the spinal cord. It may also clarify the effects of aging on spinal cord performance.

Six right sciatic nerves from adult Sprague–Dawley rats were removed within 10 minutes of cessation of cardiac activity. Once removed, the nerve was placed into saline and bubbled with 95% oxygen followed by placement into a plexiglas chamber. Two recording and stimulating electrodes were connected to the chamber and a pulse generator supplied the pulse stimuli (width = 0.02ms, amplitude = 10V) to each nerve. Each specimen was compressively loaded to a maximum of 28 grams of force and then unloaded using a small bidirectional load cell.

The action potential amplitude, width, conduction delay, and refractory periods were measured. The study showed that 27.5 grams of compression caused no recovery of the action potential. A steady decline in the action potential amplitude with an increase in the width and conduction delay was observed at 15 grams of applied load over a 60–minute time interval. Hence, compression of the neural component significantly alters the performance of the action potential prior to the threshold of compressive load (15 gms) that creates irreversible nerve conduction and structural damage.